Fossils are the preserved remains of once living things. Fossils of long-extinct species can tell us a lot about how life on Earth used to be.
Normally, when living things die, they are quickly decomposed by bacteria and fungi. On rare occasions, they can be preserved as a fossil. For this to happen, the dead organism must be quickly covered by sediment (small particles of rock) to prevent the decomposers from getting to it. The reason so many fossils are only bone is that the rest of the body is eaten or decomposed much more quickly than bone, so often only bone is left by the time the body is covered.
Fossilisation occurs when groundwater, which has minerals dissolved in it, fills in the gaps in and around the organism. The minerals sediment in the gaps, and eventually rock is formed in the shape of the organism. Sometimes fossils form around the outside of the organism, giving an impression, and sometimes they fill the spaces within the organism, giving the shape of the organism.
Fossils are rare because they rely on organisms being covered by sediment. This means that we do not have fossil samples of all the organisms that have ever existed. It is particularly difficult to find fossils of organisms that lived in areas or times where being buried in sediment was unlikely. This is why we do not have a complete fossil record.
The fossil record allows us to compare the species that existed at any given time, and see how evolution has progressed. Fossils allow us to see how our ancestors were and how we came to be. By studying fossils we can see how all life on earth descended from a single common ancestor, and how different species diverged from each other over time.
Some of the most interesting fossils we find come from dinosaurs (they’re giant reptiles: of course they’re interesting) and the early humans, like Neanderthal man. The early human fossils help us to learn where we came from.
The three levels on the exhibit cover three different periods in the Earth's history. From looking at the layer files opposite, you can see the way in which the surface features of the planet have changed over time. The PDF file below shows you a series of images, covering a time-span from over 600 million years ago, to approximately 250 million years in the future.
